Waveplate compensation in projection polarization conversion system

ABSTRACT

Three dimensional projection systems may be single projector or multiple projector systems. These 3D projection systems may include a polarization conversion system (PCS). The PCS may be designed for relatively small throw ratios and thus, may be designed to accommodate the small throw ratios. The PCS may include a polarizing beam splitter, a first optical stack, a reflector and a second quarter wave retarder. The first optical stack may include a rotator, a polarizer, a polarization switch and a first quarter wave retarder. The PCS may receive light from a projector and the PBS may direct the light toward the first optical stack. The light may be converted to a different polarization state as it passes through the first optical stack. The converted light may then be re-directed by a reflecting element to the second quarter wave retarder. The second quarter wave retarder may convert linearly polarized light to circularly polarized light.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/307,786, filed Feb. 24, 2010, entitled “Waveplatecompensation in projection polarization conversion system,” the entiretyof which is herein incorporated by reference.

TECHNICAL FIELD

The present disclosure generally relates to projection systems, and morespecifically, to stereoscopic projection systems.

BACKGROUND

Generally, polarization conversion systems (PCS) may be used for threedimensional (3D) projection as described in commonly-owned U.S. Pat. No.7,857,455 and U.S. Pub. No. 2008/0225236, which are hereby incorporatedby reference in their entirety. PCSs may be used with one or moreprojectors in a 3D projection system. One attribute of projectionsystems is the throw ratio, which may be the approximate distance fromprojector-to-screen divided by the screen width. In cinema theaters,throw ratios may typically vary from approximately 0.9 to greater than5. Other applications, such as home or office projection systems, mayhave even lower throw ratios. As throw ratio decreases, the componentsize for a PCS system may increase, possibly resulting in lesscost-effective, manufacturable, and/or saleable sizes.

BRIEF SUMMARY

According to the present disclosure, a polarization conversion systemmay include a polarizing beam splitter (PBS) operable to receiveincoming light and may separate the incoming light into a first lightbundle with a first state of polarization (SOP) and a second lightbundle with a second state of polarization (SOP) and the first SOP maybe orthogonal to the second SOP. The PCS may also include a firstoptical stack operable to receive the first light bundle from the PBS,and the first optical stack may include a rotator, a first polarizer, afirst polarization switch, and a first quarter wave retarder. Further,the PCS may include a reflector operable to receive the first lightbundle from the first optical stack, and a second quarter wave retarderoperable to receive the first light bundle from the mirror. The lens setmay be operable to receive the second light bundle from the PBS. The PCSmay further include a second optical stack operable to receive thesecond light bundle from the lens set, and the second optical stack mayinclude a second polarizer and a second polarization switch. The PBS maybe any type of PBS including a cube PBS, a wire grid PBS, a retarderbased PBS, a plate PBS and so on. The first quarter wave retarder mayhave an optic axis orientation of either one of approximately +/−45degree relative to the vertical axis and the second quarter waveretarder may have an optic axis orientation of either one ofapproximately −/+45 degree relative to the vertical axis. It should benoted that the term “vertical axis” is used for convenience in order todescribe an axis parallel to the plane of incidence on the mirror.Further, the first light bundle may be S-polarized light and the secondlight bundle may be P-polarized light.

According to another aspect, the present application discloses a methodfor providing a polarization conversion system. The method may includeproviding a polarizing beam splitter (PBS) which may be operable toreceive incoming light and may be operable to separate the incominglight into a first light bundle with a first state of polarization (SOP)and a second light bundle with a second state of polarization (SOP) inwhich the first SOP is orthogonal to the second SOP. The method may alsoinclude providing a first optical stack operable to receive the firstlight bundle from the PBS, and the first optical stack may include arotator, a first polarizer, a first polarization switch and a firstquarter wave retarder. The method may include providing a reflectoroperable to receive the first light bundle from the first optical stack,and may provide a second quarter wave retarder operable to receive thefirst light bundle from the reflector. Additionally, the method mayinclude providing a lens set which may be operable to receive the secondlight bundle from the PBS, and a second optical stack which may beoperable to receive the second light bundle from the lens set, and inwhich the second optical stack may include a second polarizer and asecond polarization switch. The first light bundle may be S-polarizedlight and the second light bundle may be P-polarized light.

According to another aspect, the present application discloses aprojection system which may include a projector which may be operable toprovide light in the direction of a projection screen, and apolarization conversion system which may be operable to receive lightfrom the projector. The polarization conversion system may include apolarizing beam splitter (PBS) which may be operable to receive incominglight and which may be operable to separate the incoming light into afirst light bundle with a first state of polarization (SOP) and a secondlight bundle with a second state of polarization (SOP), and in which thefirst SOP may be orthogonal to the second SOP. The projection system mayalso include an optical stack which may be operable to receive the firstlight bundle from the PBS, and the optical stack may include a rotator,a polarizer, a polarization switch and a first quarter wave retarder.The reflector may be operable to receive the first light bundle from theoptical stack, and a second quarter wave retarder may be operable toreceive the first light bundle from the reflector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram illustrating a conventional projectorpolarization conversion system;

FIG. 1B is a schematic diagram illustrating one embodiment of anexploded view of an optical stack;

FIG. 1C is a schematic diagram illustrating another embodiment of anexploded view of another optical stack;

FIG. 2A is a schematic diagram illustrating one embodiment of aprojector polarization conversion system, in accordance with the presentdisclosure;

FIG. 2B is a schematic diagram illustrating one embodiment of anexploded view of an optical stack, in accordance with the presentdisclosure;

FIG. 2C is a schematic diagram illustrating another embodiment of anexploded view of another optical stack, in accordance with the presentdisclosure; and

FIG. 2D is a schematic diagram illustrating another embodiment of aprojector polarization conversion system, in accordance with the presentdisclosure.

DETAILED DESCRIPTION

Various embodiments of polarization conversion systems that receivelight are described. The polarization conversion systems present abrighter image and utilize polarized light for three-dimensionalviewing.

It should be noted that embodiments of the present disclosure may beused in a variety of optical systems and projection systems. Theembodiment may include or work with a variety of projectors, projectionsystems, optical components, computer systems, processors,self-contained projector systems, visual and/or audiovisual systems andelectrical and/or optical devices. Aspects of the present disclosure maybe used with practically any apparatus related to optical and electricaldevices, optical systems, presentation systems or any apparatus that maycontain any type of optical system. Accordingly, embodiments of thepresent disclosure may be employed in optical systems, devices used invisual and/or optical presentations, visual peripherals and so on and ina number of computing environments.

Before proceeding to the disclosed embodiments in detail, it should beunderstood that the disclosure is not limited in its application orcreation to the details of the particular arrangements shown, becausethe disclosure is capable of other embodiments. Moreover, aspects of theinvention may be set forth in different combinations and arrangements todefine inventions unique in their own right. Also, the terminology usedherein is for the purpose of description and not of limitation.

FIG. 1A is a schematic diagram illustrating a conventional polarizationconversion system. Generally, a PCS may include, but is not limited to,a polarizing beam splitter, one or more reflectors, a rotator and one ormore polarization switches, arranged as shown in the various embodimentsdescribed in commonly-owned U.S. Pat. No. 7,857,455 or U.S. Pub. No.2008/0225236, both herein incorporated by reference. The PCS may alsoinclude a lens set. In one example, randomly polarized light from aprojector enters a PCS, and the randomly polarized light is separated bya polarizing beam splitter (PBS) into orthogonal polarization states,such as P and S states of polarization, and along first and secondoptical paths. Continuing the example, each of the polarized lightstates may then pass to one or more polarization switches. Thepolarization states of light in each path may be alternated in synchronywith left and right eye image frames addressed to a projector panel. Theimages from the two optical paths may be overlaid on-screen byadjustment of the reflector (or mirror) tilt and lens set magnification.A polarization preserving screen, such as a silver screen may reflectthe polarized light back to an audience, and passive eyewear, which mayinclude left and right circular polarizer stacks, may substantiallytransmit left and right imagery to the appropriate eye.

As shown in FIG. 1A, a PCS 100 may include a polarizing beam splitter110, a reflector 120, a first optical stack 130, and a screen 160.Reflector 120 may be any reflection device that directs incoming lightto another direction, such as a mirror, a prism, et cetera. FIG. 1B is aschematic diagram illustrating the first optical stack 130. The firstoptical stack 130 may include a rotator 132, a first polarizer 134, anda first polarization switch 136, arranged as shown. The rotator 132 maybe on the reflector 120 side and the first polarization switch 136 maybe located on the screen 160 side. Additionally, PCS 100 may include alens set 140 and a second optical stack 150. FIG. 1C is a schematicdiagram illustrating the second optical stack 150. The second opticalstack 150 may include a second polarizer 152 and a second polarizationswitch 152. The second polarizer 152 may be located on the lens set 140side and the second polarization switch 152 may be located on the screen160 side. The lens set 140 may be located along the second light pathand between the PBS 110 and the second optical stack 150.

In operation, randomly polarized image light energy is input to the PBS110, which may separate the incoming randomly polarized light intoorthogonal polarization states, such as an S-state of polarization and aP-state of polarization. At the PBS interface, the S- and P-polarizedlight states are directed along different light paths, on a first lightpath and a second light path. After leaving the PBS 110 through an exitport, the S-state polarized light may encounter a reflector 120. Thereflector 120 directs the incoming polarized light to the first opticalstack 130. The reflector 120 may be a mirror, but typically, metalmirrors may reflect S- and P-polarization states with differentefficiencies. Additionally, a non-zero phase difference may also begenerated between S- and P-polarization states on reflection. For acircular polarization state incident on the mirror, the resultingreflected state may no longer be circular but may be undesirably skewedinto elliptically polarized light. When sent to the screen and viewedthrough passive eyewear that is designed to filter circularly polarizedlight, this resulting undesirable elliptical state of polarization willproduce less transmitted light to the intended eye and more leakagelight to the unintended eye. The effect is a lowering of brightness andan increase in leakage, crosstalk, or ghosting in the 3D imagery.

In one embodiment employing polarization switches and as shown in FIGS.2A, 2B, 2C, and 2D, the circular polarization states incident on themirror may instead be converted to linear states, and may be orientedalong the eigenpolarizations of the mirror. Stated differently, thelinear polarization states may be oriented approximately parallel orperpendicular to the plane of incidence. In one example, this may beaccomplished by placing a passive zero-order quarter waveplate betweenthe polarization switch and mirror, and orienting the quarter waveplateapproximately parallel to the rubbing direction of at least one of theZScreen pi-cells. Further, the PCSs of FIGS. 2A, 2B, 2C, and 2D mayemploy active polarization switches and waveplate compensation around aturn mirror. In each of the systems of FIGS. 2A, 2B, 2C, and 2D,optionally, a linear polarizer may be added prior to the polarizationswitch to increase the polarization purity of the light and enhance thefinal system contrast. The term quarter waveplate may be used herein forpurposes of discussion only, and may also be used interchangeably withquarter wave plate.

The polarization switch may function as a quarter wave retarder with anapproximately 90-degree switchable orientation, thus one of these statesmay be crossed with the passive QW retarder. The result may be anapproximately linear state for most or all visible wavelengths, and maythus, result in little to no opportunity for the mirror to distort thestate of polarization. The alternate state may approximately correspondto the sum of LC QW and passive QW retardation or a net zero-orderhalf-wave, and may result in a polarization state that may be linear fora single wavelength. Since the SOP may be, in general, mixed at themirror, the polarization can be distorted, and may result withimplications on system contrast. Some examples of polarization switchesmay include, but are not limited to, the ZScreen, for example, as taughtin commonly-owned U.S. Pat. No. 7,477,206, and Achromatic PolarizationSwitches, as described in commonly-owned U.S. Pat. No. 7,528,906, whichis hereby incorporated by reference in its entirety.

By employing a zero-order quarter waveplate before the mirror, assumingthe mirror is not polarization preserving, the contrast from thereflected path may be different for each eye. In this example, thezero-order quarter waveplate may be a zero-order quarter wave retarder.Since the ZScreen modulator may be chromatic, it may be difficult toproduce two perfect orthogonal linear states at the mirror. However, itmay be possible to balance the contrast between the two states. By usingan achromatic quarter wave retarder, the dispersion may be substantiallybalanced between the two states of the ZScreen.

The quasi linearly polarized light incident on the mirror may be moreuniformly affected by the mirror properties. Generally, S- or P-linearlypolarized light may reflect from the mirror with the state ofpolarization substantially unaltered. The amplitude of the light may bereduced and the phase of the light may be changed, but these changes maynot affect the final system contrast as the linear state remainssubstantially linear and un-rotated. For systems that may employcircular polarization at the screen, a matching quarter waveplate may belocated after the mirror to substantially reinstate the circularpolarization state. Dispersion effects in the quarter waveplates may beaddressed by rotating two plates such that their fast-axes are at 90degrees to each other in the plane perpendicular to the optical path.

Note that for skew rays impinging on the mirrors, the linearly polarizedlight will still see some rotation and induced phase difference. In thiscase, the contrast will degrade, but not as significantly as whencircularly polarized light impinges on the mirror.

FIG. 2A is a schematic diagram illustrating one embodiment of aprojector polarization conversion system (PCS) 200. An embodiment of PCS200 may include a polarizing beam splitter (PBS) 210, a first opticalstack 220, a reflecting element 230, a second quarter wave retarder 240,a second optical stack 260, and a screen 270 arranged as shown. In someembodiments, the PCS 200 may also include a lens set 250. The PCS 200may receive light from a projector 205 and may transmit light to thescreen 270.

FIG. 2B is a schematic diagram illustrating an exploded view of firstoptical stack 220 shown in FIG. 2A. The first optical stack 220 mayinclude a polarization rotator 222, a first polarizer 224, a firstpolarization switch 226, and a first quarter wave retarder 228, arrangedas shown. Additionally, the first optical stack may be placed before thereflector 230 in the first optical path. Such placement may be desirablein projection systems with smaller throw ratios.

FIG. 2C is a schematic diagram illustrating an exploded view of secondoptical stack 260 shown in FIG. 2A. The second optical stack 260 mayinclude a second polarizer 262 (on the lens set 250 side) and a secondpolarization switch 264 (on the screen 270 side), arranged as shown. Insome embodiments, the first optical stack 220 of FIGS. 2A and 2B may bearranged as shown, or in other embodiments, elements of the firstoptical stack 220 may be absent and/or additional elements may beincluded. In one example, the first polarizer 224 may be omitted fromthe first optical stack 220 and/or the second polarizer 262 may beomitted from the second optical stack 260. Furthermore, the elements ofthe first optical stack 220 may be arranged in a differentconfiguration.

In operation, randomly polarized image light energy is input from theprojector 205 and the randomly polarized light may enter the PCS 200.The randomly polarized light may then enter the PBS 210. The PBS 210separates the incoming randomly polarized image light energy intodifferent, orthogonal polarization states. Additionally, in one example,the PBS 210 may transmit P-polarized light toward the lens set 250 andmay reflect S-polarized light toward the first optical stack 220. Viceversa, in another example, the PBS 210 may transmit S-polarized lighttoward the lens set 250 and may reflect P-polarized light toward thefirst optical stack 220. As discussed herein, the orthogonalpolarization states may be referred to interchangeably as S-polarizedlight and P-polarized light, first light bundles and second lightbundles.

In the operation of the embodiment of FIG. 2A, the S-state polarizedlight may travel along the first light path and may be reflected throughan exit port of the PBS 210 and encounter the first optical stack 220.The S-state polarized light may then encounter the polarization rotator222 of the first optical stack 220. The S-polarized light reflected bythe PBS 210 may pass through the polarization rotator 222 and may berotated by approximately 90 degrees to match the polarization state ofthe p-polarized light. The first light path may then travel to thepolarizer 224 which may function as a clean up polarizer and may beoptionally included in the first optical stack 220. Stated differently,the polarizer 224 may be a linear polarizer which may be included priorto the polarization switch to increase the polarization purity of thelight and enhance the final system contrast. Although as discussedherein, p-polarized light may be transmitted through the PBS 210 towardthe lens set 250, while the s-polarized light may be directed toward thefirst optical stack 220, it should be apparent to a person of ordinaryskill in the art that an alternative configuration may be employed inwhich p-polarized light may be directed toward the first optical stack220, while s-polarized light may be transmitted through the PBS 210toward the lens set 250.

Next, the polarization switch 226 may receive the light from thepolarizer 224 and may selectively transform the incoming polarizedlight. As understood by one of ordinary skill in the art, the operationof the polarization switches may be substantially synchronized with theprojection of the left eye and right eye images. The light may then passto the first quarter wave retarder 228 which may convert the light to alinearly polarized light. Continuing along the first light path, thelight may encounter the reflector 230 and the reflector 230 maysubstantially redirect the linearly polarized light further along thefirst light path, towards the second quarter wave retarder 260. Thesecond quarter wave retarder 260 may convert the light to circularlypolarized light and continue directing the light toward the projectionscreen 270.

Further in the operation of FIG. 2A, P-state light may be transmittedthrough the PBS 210 and may travel along the second light path to thelens set 250. The lens set 250 may adjust the magnification of theP-state light to approximately compensate for the extra optical pathlength in the S-state light path. The light may then pass through to thesecond optical stack 250 and encounter the second polarizer 252 and thesecond polarization switch 254. As previously discussed, the secondpolarizer 252 may be a clean up polarizer. Further as previouslymentioned, the operation of the first and second polarization switchesmay be substantially synchronized with the projection of the left eyeand right eye images.

In the embodiment of FIG. 2A, the PBS 210 is depicted as a cube PBS, asmight be used in small throw ratio situations; however various types ofPBSs may be used such as, but not limited to, a plate PBS, a retarderbased PBS and a wire grid PBS. The PBS 210 in FIG. 2A may be implementedas a glass cube (with wire grid, polarization recycling film, ordielectric layers along the diagonal) to reduce astigmatism in the finalimage associated with light passing through a tilted plate. In anotherexample, the PBS plate may be constructed using a wire grid layer onglass (e.g., Proflux polarizer from Moxtek in Orem, Utah), polarizationrecycling film (e.g., Double Brightness Enhancing Film from 3M in St.Paul, Minn.), polarization recycling film on glass (for flatness), or amulti-dielectric layer on glass.

In some embodiments, the reflecting element 230 of FIG. 2A may be amirror, such as a turn mirror or fold mirror, or any type of reflectivesurface, such as a total internal reflection prism.

In some embodiments, the polarization rotator 222 in FIGS. 2A and 2B maybe an achromatic half-wave plate. The half-wave plate may be implementedwith polymer films (e.g., Achromatic Retardation Plate), quartz plates,printed retarder material, or a static liquid crystal device optionallypattered to account for geometric polarization alternation. Thepolarization rotator 222 may be positioned as shown in FIG. 2A, or inother embodiments, it may be positioned between the reflecting element230 and the second quarter wave retarder 240. In one example, therotator 222 may be created by a laminate of polymer waveplates. Althoughin most described embodiments herein, the polarization rotator 222 islocated in the first light path, it may be placed in the second lightpath instead, and the PCS will operate in a similar manner and inaccordance with the principles of the present disclosure.

In some embodiments, the first quarter wave retarder 228 may have anoptic axis orientation of either one of approximately +/−45 degreerelative to the vertical axis. Additionally, the second quarter waveretarder 260 may have an optic axis orientation of either one ofapproximately −/+45 degree relative to the vertical axis. It should benoted that the term “vertical axis” is used for convenience in order todescribe an axis parallel to the plane of incidence on the mirror.Additionally, quarter wave retarders may be referred to herein as aquarter waveplate for purposes of discussion only, and not oflimitation. The quarter wave retarders may be in the form of a plate, adeposited material layer, or any other form that appropriately retardsthe light with respect to the optic axis.

FIGS. 2A and 2D illustrate a single and multiple projector polarizationconversion systems respectively, each of which includes polarizationswitches and waveplate compensation. FIG. 2D is a schematic diagramillustrating another embodiment of a projector polarization conversionsystem. As illustrated in FIG. 2B, a projection system may include morethan one PCS and may be used with more than one projector. FIG. 2Bincludes a first PCS 270, a first projector 275, a second PCS 280, asecond projector 285, a controller 272 and a screen 290. PCS 270 and PCS280 may each include the components of the PCS 200 of FIGS. 2A, 2B and2C.

In operation PCS 270 may receive light from the first projector 275 andPCS 280 may receive light from the second projector 285. The firstprojector 275 and the second projector 285 may be linked via thecontroller 272 which may substantially synchronize the projectioncontent and/or the left and right eye image. In one embodiment, thepolarization switches may be substantially synchronized via thecontroller 272 so that both may show the left eye image and then bothmay show the right eye image, so that the resulting brightness of theprojection system may increase. Additionally in another embodiment, thepolarization switches of the PCSs 270 and 280 may be substantiallysynchronized with the right eye image projecting from the PCS 270 andthe left eye image projecting from the PCS 280 or vice versa.

Additionally, in another embodiment for multiple projector systems andthe polarization switches may be replaced with passive waveplatecomponents. The passive waveplates may produce two distinct polarizationstates which, with matching eyewear, may substantially transmit left andright imagery to the appropriate eye after reflection from apolarization preserving screen. The projection system may not employwaveplate compensation around the reflector.

Notably, the first and second quarter waveplates are configuredorthogonally to each other (e.g., first QWP at +45 degrees, and secondQWP at −45 degrees, or vice-versa). In one embodiment of a passiveprojection system with multiple projectors, polarization switches may bereplaced with passive quarter wave retarders. The PBS may produce asubstantially linear polarization state at the reflector, and pairs ofmatching quarter wave retarders on either side of the mirror may not beemployed.

As may be used herein, the terms “substantially” and “approximately”provide an industry-accepted tolerance for its corresponding term and/orrelativity between items. Such an industry-accepted tolerance rangesfrom less than one percent to ten percent and corresponds to, but is notlimited to, component values, angles, et cetera. Such relativity betweenitems ranges between less than one percent to ten percent.

While various embodiments in accordance with the disclosed principlesdisclosed herein have been described above, it should be understood thatthey have been presented by way of example only, and are not limitation.Thus, the breadth and scope of this disclosure should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with any claims and their equivalents issuing fromthis disclosure. Furthermore, the above advantages and features areprovided in described embodiments, but shall not limit the applicationof such issued claims to processes and structures accomplishing any orall of the above advantages.

Additionally, the section headings herein are provided for consistencywith the suggestions under 37 C.F.R. 1.77 or otherwise to provideorganizational cues. These headings shall not limit or characterize theinvention(s) set out in any claims that may issue from this disclosure.Specifically and by way of example, although the headings refer to a“Technical Field,” such claims should not be limited by the languagechosen under this heading to describe the so-called technical field.Further, a description of a technology in the “Background” is not to beconstrued as an admission that certain technology is prior art to anyinvention(s) in this disclosure. Neither is the “Summary” to beconsidered as a characterization of the invention(s) set forth in issuedclaims. Furthermore, any reference in this disclosure to “invention” inthe singular should not be used to argue that there is only a singlepoint of novelty in this disclosure. Multiple inventions may be setforth according to the limitations of the multiple claims issuing fromthis disclosure, and such claims accordingly define the invention(s),and their equivalents, that are protected thereby. In all instances, thescope of such claims shall be considered on their own merits in light ofthis disclosure, but should not be constrained by the headings set forthherein.

1. A polarization conversion system comprising: a polarizing beamsplitter (PBS) operable to receive incoming light and separate theincoming light into a first light bundle with a first state ofpolarization (SOP) and a second light bundle with a second state ofpolarization (SOP), wherein the first SOP is orthogonal to the secondSOP; a first optical stack operable to receive the first light bundlefrom the PBS, wherein the first optical stack comprises a rotator, afirst polarizer, a first polarization switch, and a first quarter waveretarder; a reflector operable to receive the first light bundle fromthe first optical stack; and a second quarter wave retarder operable toreceive the first light bundle from the reflector.
 2. The polarizationconversion system of claim 1 further comprising a lens set operable toreceive the second light bundle from the PBS.
 3. The polarizationconversion system of claim 2, further comprising a second optical stackoperable to receive the second light bundle from the lens set, whereinthe second optical stack further comprises a second polarizer and asecond polarization switch.
 4. The polarization conversion system ofclaim 1, wherein the PBS is a cube PBS.
 5. The polarization conversionsystem of claim 1, wherein the first quarter wave retarder has anapproximately +45 degree configuration relative to the optic axis of thefirst polarizer.
 6. The polarization conversion system of claim 5,wherein the second quarter wave retarder has an approximately −45 degreeconfiguration relative to the optic axis of the first polarizer.
 7. Thepolarization conversion system of claim 1, wherein the first lightbundle is S-polarized light and wherein the second light bundle isP-polarized light.
 8. The polarization conversion system of claim 1,wherein the PBS is a wire grid PBS.
 9. The polarization conversionsystem of claim 1, wherein the PBS is a retarder based PBS.
 10. Thepolarization conversion system of claim 1, wherein the rotator is anachromatic half-wave plate.
 11. The polarization conversion system ofclaim 3, wherein the first polarization switch and the secondpolarization switch are substantially synchronized to alternatelyproject left and right eye images.
 12. A waveplate compensation methodfor providing a polarization conversion system, the method comprising:receiving incoming light at a polarizing beam splitter (PBS) wherein thePBS separates the incoming light into a first light bundle and a secondlight bundle; receiving the first light bundle from the PBS at a firstoptical stack wherein the first optical stack further comprises, arotator, a first polarizer, a first polarization switch and a firstquarter wave retarder; receiving the first light bundle from the firstoptical stack at a reflecting element; and receiving the first lightbundle from the reflecting element at a second quarter wave retarder.13. The waveplate compensation method of claim 12, wherein the firstlight bundle has a first state of polarization (SOP) and the secondlight bundle has a second state of polarization (SOP) further whereinthe first SOP is orthogonal to the second SOP.
 14. The waveplatecompensation method of claim 12, further comprising receiving the secondlight bundle from the PBS at a lens set.
 15. The waveplate compensationmethod of claim 12, and a second optical stack operable to receive thesecond light bundle from the lens set, wherein the second optical stackfurther comprises a second polarizer and a second polarization switch.16. The waveplate compensation method of claim 12, wherein the firstlight bundle is S-polarized light and the second light bundle isP-polarized light.
 17. The waveplate compensation method of claim 12,wherein the rotator rotates the first light bundle by 90 degreesrelative to the optic axis.
 18. The waveplate compensation method ofclaim 12, wherein the first quarter wave retarder has an optic axisorientation of at least one of an approximately +45 degree orientationrelative to the plane of incidence and an approximately −45 degreeorientation relative to the plane of incidence.
 19. The waveplatecompensation method of claim 12, wherein the second quarter waveretarder converts the first light bundle from linearly polarized lightto circularly polarized light.
 20. A projection system comprising: aprojector operable to provide light in the direction of a projectionscreen; and a polarization conversion system operable to receive lightfrom the projector, wherein the polarization conversion system furthercomprises: a polarizing beam splitter (PBS) operable to receive incominglight and separate the incoming light into a first light bundle with afirst state of polarization (SOP) and a second light bundle with asecond state of polarization (SOP), wherein the first SOP is orthogonalto the second SOP; an optical stack operable to receive the first lightbundle from the PBS, wherein the optical stack further comprises, arotator, a polarizer, a polarization switch and a first quarter waveretarder; a reflector operable to receive the first light bundle fromthe optical stack; and a second quarter wave retarder operable toreceive the first light bundle from the reflector.